Image projection devices are widely used today in many electronic applications, such as televisions, computers, and projectors. These projection devices may employ any of several relatively new types of luminosity modulators, such as Digital Light Processing (“DLP”), Liquid Crystal Display (“LCD”), and Liquid Crystal on Silicon (“LCOS”) microdisplays to project an image onto a viewing medium, such as a television viewing panel, screen, wall, etc.
While each of these different types of luminosity modulators improves overall brightness, contrast, and resolution over prior vacuum tube, transistor, and slide projector technology, each has its own distinct drawbacks that affect the image produced on the screen. For example, a DLP microdisplay typically provides images in black and white and cooperates with hardware such as chromatic modulators in the form of color wheels to produce a spectrum of colors. However, color wheels generally pass only a single color at any given time (effectively reducing the amount of light projection by the system) and DLPs may exhibit a lower resolution than its LCD and LCOS counterparts because of the larger pixel sizes DLPs employ.
The luminosity modulators that are polarization based, such as the LCD and LCOS modulators, require the prepolarization of light to achieve some contrast between the images displayed on the screen. Prepolarization, however, generally results in the loss of about half of the light produced by a light source for image projection. Polarization recovery systems may be added to the projection system, at an added cost, to recover much of the lost light. Even with the polarization recovery systems, these modulators still exhibit a relatively low contrast, which affects theater or low ambient light viewing. Also, for these modulators to modulate color, three separate modulators are used—one for the projection of each of the colors of red, blue, and green—or the use of sequential color which requires added hardware and a further reduction in efficiency.
Optical lenses are employed with the luminosity modulators to concentrate the light transmitted to and reflected from the particular luminosity modulators. Typically, one set of optical lenses, “illumination lenses,” transmits the light to the luminosity modulators and a second set of optical lenses, “projection lenses,” receives the reflected light from the luminosity modulators and projects the image on to a viewing medium. The use of multiple sets of lenses to separately accomplish illumination and projection adds significant complexity to the design of a projector or television as well as added costs to the overall system.
The embodiments described hereinafter were developed in light of this situation and the drawbacks associated with existing systems.